Identifying medium and identifying method for object

ABSTRACT

The present invention provides a discrimination medium A for discriminating the authenticity of an article by providing an optically discriminating mark on the article. A film  20  having a light reflecting layer of a polymer cholesteric liquid crystal having a circular polarization light selectivity for reflecting a specific circular polarization light is fixed to a part of the surface of a support  10 . A printed portion is made by printing on the portions other than the film  20  of the support  10  in substantially the same color as that shown when the film  20  is viewed from the front. The discrimination medium A appears to be red at the support  10  and the film  20  when viewed from the front (although the film has a metallic luster), but at a larger viewing angle, the film  20  changes to blue by the blue-shift of the polymer cholesteric liquid crystal so as to exhibit a color different from that of the support  10.

TECHNICAL FIELD

The present invention relates to a discrimination medium for determiningwhether two-dimensional articles such as packages in which goods arepacked, passports, cards, bills, exchange tickets for money, bonds,security notes, gift certificates, pictures, tickets, public game votingtickets, etc. are authentic, and for determining various kinds ofthree-dimensional articles are authentic.

BACKGROUND ART

Conventionally, for example, a technique of pasting a hologram on asurface of an article or a technique of applying special ink on asurface of an article have been known as methods for anti-falsificationof articles such as cards and security notes. In a technique in whichthe hologram is used, the authenticity of the article on which thehologram is pasted is determined by viewing the hologram, which appearsto be three-dimensional or varies in color depending on the viewingangle. In a technique in which the special ink is used, for example,fluorescent ink or magnetic ink may be used as the special ink. Theauthenticity of the article on which the above ink is applied isdetermined by sensing information hidden in the above ink by irradiatingultraviolet light thereon or by magnetic sensors although the above inkmay be viewed in the same manner as normal inks.

However, the above falsification techniques have become moresophisticated as hologram manufacturing techniques have come into wideuse, it is easy to falsify the hologram, and the falsified hologramcannot thereby be distinguished from an authentic one. In addition,since it is easy to obtain inks similar to the fluorescent ink or themagnetic ink, it is easy to falsify the ink, and a device for sensinginformation hidden in the above ink is very large and requires a powersupply. Due to this, it is difficult to employ the technique using theabove ink.

A technique in which a seal having a reflecting layer composed of acholesteric liquid crystal is adhered on an article is disclosed inJapanese Unexamined Patent Application Publication No. 4-144796. Thecholesteric liquid crystal has a circular polarization lightselectivity, has metallic luster, and varies in color depending on theviewing angle (blue shift), and is thereby anticipated as a medium fordistinguishing articles. However, in the conventional technique, theentire medium is composed of the cholesteric liquid crystal and equallythereby exhibits blue shift. Due to this, there is nothing therearoundwhich the medium of the cholesteric liquid crystal may be comparedtherewith in color, and only sensory judgment of the authenticity of thearticle can thereby be performed, and it is thereby difficult todistinguish. As a result, it is difficult to reliably confirm theauthenticity of an article by simply viewing the article from onedirection. In addition, since the entire discrimination medium iscomposed of the cholesteric liquid crystal, the manufacturing cost isgreatly increased. Alternatively, there is a case of pasting a seal on apackage in which articles such as goods are packed. However, if packagesdiscarded by a user are stolen, falsified goods packed in the stolenpackages may be sold, or if a seal is peeled off from a package,falsified goods packed in another package on which the stolen seal ispasted may be sold.

Therefore, objects of the present invention are to provide adiscrimination medium which can prevent falsification, facilitatesdetermining the authenticity of the articles reliably and enablesreduction in the manufacturing cost, and to provide a discriminationmethod using the same.

DISCLOSURE OF THE INVENTION

The present invention provides a discrimination medium for determiningthe authenticity of an article by providing an optically distinguishablemark on the article, comprising: a support; a film fixed at a part of asurface of the support, the film having a light reflecting layercomposed of a polymer cholesteric liquid crystal having a circularpolarization light selectivity for reflecting a specific circularpolarization light; and a printed portion printed at a part of thesupport's surface other than the film, the printed portion havingsubstantially the same color as that shown when the film is viewed froma predetermined direction.

The fundamental principle of the present invention will be describedhereinafter. FIG. 1 schematically shows a structure of a cholestericliquid crystal. The cholesteric liquid crystal has a layered structure.The molecular long axial directions of the respective layers of thelayered structure are parallel to each other and are parallel to theplane thereof. The respective layers are rotated slightly with respectto the adjacent layer so as to be stacked, and the cholesteric liquidcrystal thereby has a three-dimensional spiral structure. Assuming thatpitch P is a distance needed when a direction factor of the molecularlong axis direction is rotated through 360 degrees and is restored to aninitial state and an average refractive index of the respective layersis index N, the cholesteric liquid crystal selectively reflects specificcircular polarization light having a center wavelength λs satisfying theequation λs=N×P (circular polarization light selectivity). Therefore, asshown in FIG. 2, when the molecular long axis direction of therespective layers of the cholesteric liquid crystal is rotated in aclockwise direction with respect to incident light, right-handedcircular polarization light having a center wavelength λs is reflectedby the cholesteric liquid crystal as it is, and left-handed circularpolarization light passes though the cholesteric liquid crystal. On theother hand, all light other than the left-handed circular polarizationlight passes through the cholesteric liquid crystal. For example,cholesteric liquid crystal reflecting light of a red center wavelengthλs may be placed on a material, which is absorbing visible light, suchas a black sheet. When the cholesteric liquid crystal on the material isexposed to random polarization light such as sunlight, only right-handedcircular polarization light of a center wavelength λs is reflected bythe cholesteric liquid crystal, light transmitted thorough thecholesteric liquid crystal is absorbed by the black sheet, and thecholesteric liquid crystal thereby appears to be clearly red.

The cholesteric liquid crystal changes color depending on the viewangle. When incident light obliquely enters into the cholesteric liquidcrystal, the apparent pitch P decreases, and the center wavelength λs isthereby short. For example, the color of light, which is reflected bythe cholesteric liquid crystal which has a red color when incident lightentering perpendicularly thereto is observed, shifts to orange, yellow,green, blue-green, and blue in turn (blue shift).

According to the discrimination medium for determining the authenticityof an article of the present invention, the film having a lightreflecting layer composed of a polymer cholesteric liquid crystal havingin turn a circular polarization light selectivity of reflecting aspecific circular polarized light is fixed at a part of a surface of thesupport and a printed portion is printed at a part of the support'ssurface other than the film having substantially the same color as thatshown when the film is viewed from a predetermined direction, wherebythe film reflects a specific circular polarization light, and thesurroundings of the film, that is, the printed portion reflects randompolarization light. As a result, the color of the film changes by theblue shift and the color of the surroundings do not change at a largerviewing angle, whereby the film gradually stands out from thesurroundings, although the film has substantially the same color as thesurroundings and the border between the film and the surroundings is notvery obscure when the discrimination medium is viewed from apredetermined direction. Therefore, anyone can easily and reliablydistinguish the discrimination medium by viewing. A part of thediscrimination medium is composed of the cholesteric liquid crystal,whereby the manufacturing cost can be reduced.

In the present invention, the discrimination medium can be distinguishedmore reliably by using optical filters. That is, the discriminationmedium of the present invention can be viewed via a first filter and asecond filter so as to distinguish the article. The first filter canallow only circular polarization light having the same polarizationdirection as circular polarization light from the light reflecting layerto pass therethrough. The second filter can allow circular polarizationlight having a polarized direction opposite to the circular polarizationlight from the light reflecting layer to pass therethrough. In thiscase, when the article on which the discrimination medium is provided isviewed via the first filter, the part other than the film can reflectrandom polarization light, whereby the color of the printed portion canbe observed. In the film, only a specific circular polarization light(for example, right-handed circular polarization light) can pass throughthe first filter, only the specific wavelength light of the specificcircular polarization light can be reflected by the light reflectinglayer of the film, and can pass through the first filter again, wherebythe film can be observed more clearly via the first filter and can standout with respect to the printed portion therearound. When the view angleis larger, the cholesteric liquid crystal can turn to a different colorfrom the surroundings by the blue shift. In addition, since the secondfilter does not allow circular polarization light having the samepolarization direction as circular polarization light from the lightreflecting layer to pass therethrough, the cholesteric liquid crystalappears brack via the second filter and the surroundings have the colorof the printed portion.

On the other hand, when, for example, ink is printed instead of thefilm, random polarization natural light reflects thereon, circularpolarization light of random polarization natural light, which have thesame polarization direction as circular polarization light from thereflecting layer, can pass through the first filter, and circularpolarization light polarized in a direction opposite to the circularpolarization light from the light reflecting layer can pass through thesecond filter. These circular polarization lights are composed of lightof every wavelength, and right-handed and left-handed circularpolarization lights are included by almost the same amount. Therefore,the same article can be observed via the first filter and the secondfilter, and the article can be confirmed as a fake.

When a discrimination mark, which is composed of the cholesteric liquidcrystal film having circular polarization light selectivity opposite tothat of the authentic discrimination mark, is formed, the cholestericliquid crystal film and the surroundings therearound can be viewed viathe first filter and the second filter in the opposite manner to that ofthe above case. That is, the cholesteric liquid crystal can appear blackand the surroundings can appear to be the printed color since thesurroundings reflects random polarization light. In the second filter,the film can be observed more clearly than the surroundings, and whenthe view angle is larger, the film can be observed differently by theblue shift. Therefore, in this case, the article can be distinguished asbeing falsified one.

In the discrimination medium of the present invention, the film of thecholesteric liquid crystal can be cut in a predetermined shape and maybe arranged on the support, whereby the film can have a predeterminedpattern portion, a predetermined figure portion or a predeterminedcharacter portion. The discrimination medium of the present inventionfurther may comprise a hologram formed by embossing the surface or therear face of the film.

According to the present invention, it is difficult to falsify thediscrimination medium. That is, since the cholesteric liquid crystalhaving substantially the same color as the printed portion printed onthe support needs to be copied, be cut, and be arranged on the supportso as to have a predetermined shape, it is very difficult to falsify thediscrimination medium. In addition, in order to prevent falsification,the following example can be applied to the present invention.

For example, the discrimination medium may further comprise: an adhesiveprovided on the rear face of the support so that the support is pastedon the article via the adhesive; and a gap so that the discriminationmedium tears when the support is detached from the article. In addition,the discrimination medium may further comprise: an adhesive provided onthe rear face of the support so that the support is pasted on thearticle via the adhesive, wherein a part of the adhesive remains adheredon the article when the support is detached from the article, wherebythe remaining part of the adhesive on the article shows that the supporthas been detached from the article. For example, a message such as“opened” may be visible on the discrimination medium. According to thepresent invention, it is impossible to peel off the discriminationmedium from a discarded package in order to use the discriminationmedium.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective diagram showing a cholesteric liquid crystal forexplaining a principle of the present invention.

FIG. 2 is a perspective diagram showing a circular polarization lightreflected on the cholesteric liquid crystal.

FIG. 3 a perspective diagram showing a discrimination medium and acircular polarization light filter.

FIG. 4A is a side view showing a manufacturing device for thediscrimination medium of an embodiment according to the presentinvention, FIG. 4B is a cross sectional diagram showing details of asupport, and FIG. 4C is a cross sectional diagram showing details of afilm.

FIG. 5 is a plane view showing a discrimination medium in which a gap isprovided.

FIG. 6A is a perspective view showing a state in which thediscrimination medium is pasted on a package, and FIG. 6B is aperspective view showing a state in which the package is opened.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment will be explained hereinafter.

A polymer cholesteric liquid crystal can be manufactured by methodsdescribed in, for example, Japanese Unexamined Patent ApplicationPublication No. 63-51193, Japanese Unexamined Patent ApplicationPublication No. 57-165480, and Japanese Unexamined Patent ApplicationPublication No. 58-17119. For example, low molecular cholesteric liquidcrystal is dissolved and maintained in a polymerized monomer, wherebycholesteric liquid crystals grow. The low molecular cholesteric liquidcrystals are joined by photoreaction or thermal reaction. As a result,the molecular orientation thereof is fixed and the low molecularcholesteric liquid crystals are formed into a polymer thereof.Alternatively, thermo-tropic polymer liquid crystal of branched-chaintype or straight-chain type may be heated above the transition pointthereof so that a cholesteric liquid crystal structure thereof may grow,and may be then cooled to a temperature below the transition pointthereof so that the molecular orientation thereof may be fixed.Alternatively, lyotropic liquid crystal of the branched-chain type orstraight-chain type may be oriented in a solvent in a cholestericorientation, and the solvent is gradually volatilized so that molecularorientation thereof is fixed.

For example, a branched-chain type polymer having a liquid crystalforming group in a branched-chain such as acrylic resin, polymethylmethacrylate, polysioxane, polymeronate and a straight-chain typepolymer having liquid crystal forming group in a branched-chain such aspolyester, polyester amide, polycarbonate polyamide and polyimide may bementioned as a polymer cholesteric liquid crystal.

The above polymer cholesteric liquid crystal can be produced by coatingraw material liquid on one side of a thin plastic film (for example,polyethylene terephthalate (PET) film) having a peeling layer and fixingcholesteric orientation and molecular orientations, and so on. In thiscase, the polymer cholesteric liquid crystal has equal torsion pitch Pextending in a layered direction thereof and has a thickness of 0.5 to5.0 μm. Black heat seal (thermal fusion adhesive) is coated on thepolymer cholesteric liquid crystal and is slit into a film having 1 to 5mm thickness by a micro-slitter.

A support can be composed of polypropylene, polyester, PET, TAC(triacetylcellulose), and a sheet. A printed portion havingsubstantially the same color (for example, red) as the film when viewedfrom the front thereof is printed on the support, the above film ispositioned on the printed portion, and the heat seal is heated on thefilm so as to fix the film. The plastic film is peeled off so that thecholesteric liquid crystal film is exposed. The black heat seal is usedin order to absorb light passing through the polymer cholesteric liquidcrystal. A thin overcoat layer may be provided between the plastic filmand the polymer cholesteric liquid crystal and is exposed on the surfaceafter peeling off the plastic film.

FIG. 3 is a schematic diagram showing a method of discriminating anarticle by using a discrimination medium A having a support 10 and afilm 20 of a cholesteric liquid crystal which is fixed at the support 10in the above manner, and a circularly polarization light filter 2.Although the support 10 and the film 20 appear to be red when viewedfrom the front of the discrimination medium A, the color of the film 20changes to blue at a larger viewing angle. The circular polarized lightfilter 2 has a first filter 2 a allowing only right-handed circularpolarization light to pass therethrough and a second filter 2 b allowingonly left-handed circular polarization light to pass therethrough. Thefirst filter 2 a has a wave plate 21 a and a polarization plate 22 a.The second filter 2 b has a wave plate 21 b and a polarization plate 22b. The polarization plates 22 a and 22 b allow light having a specificwave direction to pass therethrough so as to change the light intolinearly polarized light. The wave plates 21 a and 21 b shift phase ofpart of the linearly polarized light by quarter wavelength thereof so asto change the linearly polarized light to the circular polarizationlight. In this embodiment, light entering from the polarization plate 22a changes from the light linearly polarized by the first filter 2 a toright-handed circular polarization light. On the other hand, lightentering from the polarization plate 22 a changes from the lightlinearly polarized by the second filter 2 b to left-handed circularpolarization light. The wave plates 21 a and 21 b change circularpolarization light entering thereinto to linearly polarized light andchange linearly polarized light entering thereinto to circularpolarization light.

In the right-handed circular polarization light exiting from the firstfilter 2 a, the component of the wavelength thereof depending on thepitch is reflected by the film 20, and enters into the first filter 2 aagain remaining the right-handed circular polarization light. Theright-handed circular polarization light is converted by the firstfilter 2 a to the linearly polarized light and exits therefrom. Sincethe random polarization light is reflected by the surface of the support10, the right-handed circular polarization light thereof passes throughthe first filter 2 a and the printed portion thereby appears to be red,for example. In the film 20, only the right-handed circular polarizationlight passes through the first filter 2 a, and for example, the redwavelength light thereof is reflected by the light reflecting layer ofthe film 20 and passes through the first filter 2 a again. As a result,the film 20 appears to be more distinct when viewed via the first filter2 a and the film stands out against the surrounding printed portion. Thechoresteric liquid crystal exhibits the blue shift so that the film 20appears to be a different color from the surroundings thereof The film20 appears to be black when viewed via the second filter 2 b since thesecond filter 2 b does not pass through the circular polarization lighthaving the same polarization direction as circular polarization lightfrom the light reflecting layer and the surroundings thereof appears tobe red since the random polarization light is reflected on surroundingsthereof. Therefore, the article can be distinguished as an authentic onebased on the above appearance of the discrimination medium A which isdifferent between via the first filter 2 a and via the second filter 2b.

On the other hand, when, for example, ink is printed instead of the film20, random polarization natural light is reflected thereby, circularpolarization light of random polarization natural light, which have thesame polarization direction as circular polarization light from thereflecting layer, passes through the first filter 2 a, and circularpolarization light polarized in a direction opposite to the circularpolarization light from the light reflecting layer passes through thesecond filter 2 b. These circular polarization lights are composed oflight of all wavelengths, and right-handed and left-handed circularpolarization light are included in almost the same amount. Therefore,the same article can be observed via the first filter 2 a and the secondfilter 2 b, and the article can be confirmed as being a fake.

When discrimination medium A composed of the cholesteric liquid crystalfilm 20 having circular polarization light selectivity opposite to theaustenitic one is formed, the cholesteric liquid crystal film and thesurroundings therearound can be viewed via the first filter 2 a and thesecond filter 2 b in an opposite manner to that of the above case. Thatis, the cholesteric liquid crystal can appear to be black and thesurroundings can be observed in the printed color since the surroundingsreflect random polarization light. In the second filter 2 b, the film 20can be observed more clearly than the surroundings, and when the viewangle is larger, the film can be observed differently by the blue shift.Therefore, in this case, the article can be distinguished as a fake one.

The manufacturing method of the above discrimination medium A will beexplained hereinafter with reference to FIGS. 4A to 4C. As shown in FIG.4B, the support 10 is equipped with a substrate 11 of a PET film, anadhesive layer 12 layered on the rear face of the substrate 11, apeeling sheet 13 layered on the rear face of the adhesive layer 12 and ared printed layer 14 layered on the surface of the substrate 11. Asshown in FIG. 4C, the film 20 is equipped with a peeling layer 22, apolymer cholesteric liquid crystal layer 23 and a black heat seal layer24 which are layered in turn on a rear face of a substrate 21. The film20 has a belt-like body of a few mm in width.

As shown in FIG. 4A, reference numeral 30 denotes a first roller forrolling the support 10, 31 denotes a second roller for rolling the film20. Plural second rollers 31 are located in a width direction which isperpendicular to a sheet. The support 10 and the film 20 are fixed toeach other by melting the heat seal layer 24 with a thermo compressionbonding roller 32. Next, the substrate 21 is peeled from the film 20 andis rolled by a first rolling roller 33.

Next, the film 20 is cut in half by metallic molds 34 and 35 so as tohave the peeling sheet 13 of the support 10 and to have a predeterminedlength. The part 25 other than the discrimination mediums A, which hasthe support 10 and the film 20 and which is cut in a rectangular shapethereafter, is then rolled by a second rolling roller 36. Next, thediscrimination mediums A are cut by a slitter 37 among each other andare rolled separately as a belt by a third rolling roller 38. The thirdrolling roller 38 rolling and have the discrimination mediums A ismounted to a mounting device as it is, and the discrimination mediumsare pasted onto article packages mechanically.

As shown in FIG. 5, when the discrimination mediums A are cut in half bythe metallic molds 34 and 35, gaps 26 can be formed on thediscrimination mediums A. In a case in which the discrimination medium Ais pasted onto the corner of the package P as shown in FIG. 6A, thediscrimination medium A is torn at the gap 26 as shown in FIG. 6B andcannot thereby be reused when the package P is opened. When thediscrimination medium A is detached from the package P, thediscrimination medium A is also torn at the gap 26.

According to the discrimination medium of the present invention asdescribed above, the film, which has a light reflecting layer composedof a polymer cholesteric liquid crystal having a circular polarizationlight selectivity of reflecting a specific circular polarization light,is fixed at a part of the surface of the support, and the printedportion, which has substantially the same color as that shown when thefilm is viewed from the front thereof, is printed at a part of thesupport's surface other than the film, whereby the discrimination mediumcan prevent falsification, can be easily and reliably visuallydistinguished, and the manufacturing cost can be reduced.

1. A discrimination method for determining the authenticity of anarticle by providing an optically discriminating mark having a figureportion or a character portion on the article, the discrimination methodcomprising steps of: fixing a film at part of the surface of a support,the film having a light reflecting layer composed of a polymercholesteric liquid crystal having a circular polarization lightselectivity for reflecting a specific circular polarization light;making the film smaller than the support; printing a printed portion atanother part of the support's surface in substantially the same color asa color of the film when the film is viewed from a predetermineddirection, the another part being other than the part at which the filmis fixed; providing the support to the article as the discriminatingmark; and viewing the discriminating mark via a first filter and asecond filter, the first filter allowing only predetermined circularpolarization light having a same polarization direction as circularpolarization light from the light reflecting layer to pass therethrough,the second filter allowing circular polarization light having apolarized direction opposite to the predetermined circular polarizationlight from the light reflecting layer to pass therethrough, wherein thediscriminating mark is viewed via the first filter, the color of theprinted portion is not changed regardless of a change of the view angle,and the color of the film is changed by blue shift of a color of thelight reflecting layer in accordance with the change of the view angle,and wherein the discriminating mark is viewed via the second filter, thecolor of the printed portion is not changed regardless of the change ofthe view angle, and the color of the film is black regardless of thechange of the view angle, so that the authenticity of the article isdetermined.
 2. A discrimination medium for determining the authenticityof an article by providing an optically discriminating mark on thearticle, comprising: a support; a film fixed at a part of a surface ofthe support, the film having a light reflecting layer composed of apolymer cholesteric liquid crystal having a circular polarization lightselectivity of reflecting a specific circular polarization light; aprinted portion at another part of the support's surface, the anotherpart being other than the part at which the film is fixed; an adhesiveprovided on a rear face of the support so that the support is pasted onthe article via the adhesive, the rear face being opposite to thesurface; and a gap formed on the support for allowing the discriminationmedium to tear when the support is detached from the article, whereinthe printed portion has substantially the same color as a color of thefilm when the film is viewed from a predetermined direction, the colorof the printed portion is not changed regardless of the change of theview angle, and the color of the film is changed by blue shift of acolor of the light reflecting layer in accordance with the change of theview angle.
 3. The discrimination medium according to claim 2, whereinthe film has plural portions cut in a predetermined shape and the pluralportions of the film are arranged on the support, whereby the film has apredetermined pattern portion, a predetermined figure portion, or apredetermined character portion.
 4. The discrimination medium accordingto claim 2, the discrimination medium further comprising: a hologramformed by executing embossing of the surface or the rear face of thefilm, the rear face being opposite to the surface.
 5. A discriminationmedium for determining the authenticity of an article by providing anoptically discriminating mark on the article, comprising: a support; afilm fixed at a part of a surface of the support, the film having alight reflecting layer composed of a polymer cholesteric liquid crystalhaving a circular polarization light selectivity of reflecting aspecific circular polarization light; a printed portion at another partof the support's surface, the another part being other than the part atwhich the film is fixed; and an adhesive provided on a rear face of thesupport so that the support is pasted on the article via the adhesive,the rear face being opposite to the surface, wherein the printed portionhas substantially the same color as a color of the film when the film isviewed from a predetermined direction, the color of the printed portionis not changed regardless of the change of the view angle, and the colorof the film is changed by blue shift of a color of the light reflectinglayer in accordance with the change of the view angle, wherein a part ofthe adhesive remains adhered on the article when the support is detachedfrom the article, whereby the remaining part of the adhesive on thearticle shows that the support has been detached from the article. 6.The discrimination medium according to claim 5, wherein the film hasplural portions cut in a predetermined shape and the plural portions ofthe film are arranged on the support, whereby the film has apredetermined pattern portion, a predetermined figure portion, or apredetermined character portion.
 7. The discrimination medium accordingto claim 5, the discrimination medium further comprising: a hologramformed by executing embossing of the surface or a rear face of the film,the rear face being opposite to the surface.